(The following report by Alex Rodriguez appeared on the Chicago Tribune website on August 15.)

MOSCOW— Russian investigators Tuesday launched a terrorism investigation into a bomb blast that derailed an express train from Moscow to St. Petersburg, injuring more than 60 people traveling on one of the country's busiest rail routes.

The explosion occurred late Monday near the city of Novgorod, about 300 miles northwest of Moscow. Investigators said they believe a homemade bomb placed beneath the tracks was detonated by remote control as the Nevsky Express train passed by with 251 people aboard.

The blast tore a 3-foot-wide gap in the rail line just 100 feet before a bridge. However, because the train was traveling at 80 m.p.h., it had enough momentum to cross the bridge before derailing, Russian authorities said.

Though no one was killed, the blast unnerved a nation that has seen a lull in terrorist activity outside the volatile North Caucasus region in the past couple of years.

Nikolai Patrushev, director of the Federal Security Service, the KGB's successor agency, said at a national anti-terrorist committee meeting in Moscow that "the threat of extremism and terrorism has not been completely eliminated."

The bomb blast near Novgorod mirrored the attack on a train traveling from Grozny to Moscow on June 12, 2005, in which a remote-controlled bomb planted on a stretch of track near the capital derailed the train and injured 42 people. In April, two Russian ultranationalists were convicted of engineering the attack.

No one had claimed responsibility for the blast near Novgorod as of Tuesday evening. In the past, separatist rebels fighting for Chechnya's independence from Russia have been linked to a litany of terrorist attacks, including the 2002 takeover of a Moscow theater that killed 129 hostages and the 2004 school siege in Beslan that killed 331 people, 186 of them children.

In December 2003, Chechen separatists were blamed for a bomb blast that killed 47 people on a train traveling from Kislovodsk to Mineralny Vody in southern Russia.

The train targeted Monday, the Nevsky Express, is popular with foreign tourists traveling between St. Petersburg and Moscow, though there were no reports of any foreigners injured in the blast.

Crew members interviewed on Russian television said nearby villagers and passengers broke through the windows of the toppled cars to free those trapped inside.

"I heard an explosion, felt the railway car shaking, and then it fell off the rails," said Larisa Panteleyeva, a waitress in the restaurant car. "The car apparently rolled over, though I really don't remember."

Russian authorities said that of the 60 people injured, 25 were hurt seriously enough to be hospitalized. Five people were listed in critical condition.

Television footage from the scene showed a 5-foot-wide crater where the blast occurred, and what appeared to be frayed wire by the broken rail line. At least a half-mile of track was destroyed.

Investigators said they found a wire leading to a nearby thicket, where they believe someone may have detonated the bomb by remote control. About 4 1/2 pounds of TNT were used in the blast, investigators said.